Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

A method and composition for the reduction of the emission of selenium
into the environment from the burning of fossil fuels with the use of two
chemistries, either individually or in combination with each other. The
method uses polydithiocarbamic compounds, including polydithiocarbamic
compounds derived from a polymer produced from acrylic-x and alkylamine
in conjunction with a scrubber process to capture selenium and reduce its
emission in aqueous phase blowdown. The method and composition also helps
reduce corrosion in the scrubber process.

Claims:

1. A composition of matter comprising: a polydithiocarbamic compound of
at least one polythiocarbamic material; and a transition metal salt.

2. The composition of claim 1, wherein the composition additionally
comprises a polymer derived from at least two monomers: acrylic-x and an
alkylamine, and wherein said acrylic-x has the following formula:
##STR00005## wherein X═OH and salts thereof or NHR2 and wherein
R1 and R2 is H or an alkyl or aryl group, wherein the molecular
weight of said polymer is between 500 to 200,000, and wherein said
polymer is modified to contain a functional group capable of scavenging
at least one metal-comprising composition.

3. The composition of claim 2, wherein the polydithiocarbamic compound is
the polymer.

5. The composition of claim 1, wherein the polydithiocarbamic compound
has a molecular weight of 500 to 100,000 Da.

6. The composition of claim 1, wherein the transition metal salt is an
iron salt.

7. The composition of claim 1, wherein the transition metal salt is a
manganese salt.

Description:

[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 11/952,637, filed Dec. 7, 2007, and of U.S. patent
application Ser. No. 12/754,683, filed Apr. 6, 2010, the disclosures of
which are herein incorporated by reference.

COPYRIGHT NOTICE

[0002] A portion of the disclosure of this patent document contains or may
contain copyright protected material. The copyright owner has no
objection to the photocopy reproduction by anyone of the patent document
or the patent disclosure in exactly the form it appears in the Patent and
Trademark Office patent file or records, but otherwise reserves all
copyright rights whatsoever.

TECHNICAL FIELD

[0003] This invention relates to the treatment of flue gas wet scrubber
processes. More particularly, the invention relates to the method of
capture of selenium from flue gases by flue gas wet scrubber processes.
The invention also relates to minimizing corrosion in flue gas wet
scrubber processes.

BACKGROUND

[0004] The demand for electricity continues to grow globally. In order to
keep stride with the growing demand, coal is being looked to as a source
for its generation. At present, burning coal produces some 50% of the
electricity generated in the United States. The burning of coal in power
generation plants results in the release of energy, as well as the
production of solid waste such as bottom and fly ash, and flue gas
emissions into the environment. Emissions Standards, as articulated in
The Clean Air Act Amendments of 1990 as established by the U.S.
Environmental Protection Agency (EPA), requires the assessment of
hazardous air pollutants from utility power plants.

[0005] The primary gas emissions are criteria pollutants (e.g. sulfur
dioxide, nitrogen dioxides, particulate material, and carbon monoxide).
About two thirds of all sulfur dioxide and a quarter of the nitrogen
dioxide in the atmosphere is attributable to electric power generation
achieved by burning coal and other fuels.

[0006] Secondary emissions depend on the type of coal or fuel being
combusted but include as examples mercury, selenium, arsenic, and boron.
Selenium chemistry is similar to sulfur chemistry where selenium exists
in flue gas as selenium dioxide and immediately converts to the selenite
ion upon absorption into the liquid stream within the flue gas wet
scrubber process. While certain chemistries have been known to
successfully capture heavy metal cations, such chemistries would not
expect to be effective at reducing selenium concentrations in liquid
waste generated from flue gas wet scrubber processes.

[0007] Furthermore, because of the presence of high concentrations of
halogens in the flue gas that is transferred to the scrubber liquor, flue
gas wet scrubber processes can fail from corrosion. Recently, a
metallurgy designated as 2205 alloy stainless steel has become popular in
the industry due to its low cost and high chloride resistance. Typically,
these scrubbers will operate with 10 to 12,000 ppm chloride concentration
in their liquors. Unfortunately, flue gas wet scrubbers constructed of
2205 alloy have experienced increased levels of pitting and localized
corrosion, resulting in forced, unscheduled unit shutdowns and expensive
repairs.

[0008] One potential solution to the corrosion problem that has been
implemented commercially is the use of potential adjustment protection
("PAP") systems. PAP systems apply an electrical potential across the
metal surface in an effort to control and reduce corrosion. This method
has been successful, but it requires the installation of electrodes into
the scrubber and the constant application of electrical potential and
current. It also suffers from being applicable to only wet surfaces
within the scrubbers.

[0009] Another solution to the problem is the operation of flue gas wet
scrubbers at less than 2000 ppm chloride concentrations. While this
prolongs the time between failures, it does not completely halt
corrosion. Additionally, this solution results in higher blowdown rates,
translating into higher water usage, higher wastewater treatment costs,
and overall higher operating costs.

[0010] Consequently, there remains a need for a technology that can
cost-effectively remove selenium from flue gas in flue gas wet scrubber
processes. Ideally, the technology would have the added benefit of
minimizing corrosion in flue gas wet scrubber processes. The invention
described below addresses these needs.

SUMMARY OF THE INVENTION

[0011] The invention is directed toward a method for removing selenium
from flue gas in a flue gas wet scrubber process. The invention is also
directed toward a method for minimizing corrosion in a flue gas wet
scrubber process. Each method comprises the steps of burning fuel,
thereby producing flue gas; and passing the flue gas into the flue gas
wet scrubber process comprising a polydithiocarbamic compound of at least
one polythiocarbamic material.

[0012] In another embodiment, the method comprises the steps of burning
fuel, thereby producing flue gas; and passing the flue gas into the flue
gas wet scrubber process comprising a polymer derived from at least two
monomers: acrylic-x and an alkylamine, and wherein said acrylic-x has the
following formula:

##STR00001##

wherein X═OH and salts thereof or NHR2 and wherein R1 and
R2 is H or an alkyl or aryl group, wherein the molecular weight of
said polymer is between 500 to 200,000, and wherein said polymer is
modified to contain a functional group capable of scavenging at least one
metal-comprising composition. The method may comprise a combination of
the polydithiocarbamic compound and the polymer derived from acrylic-x
and alkylamine. The polydithiocarbamic compound may be the polymer. The
invention may further comprise a transition metal salt, which may be an
iron salt.

[0013] In a third embodiment, the invention is directed toward a
composition of matter comprising a polydithiocarbamic compound of at
least one polythiocarbamic material; and a transition metal salt.

[0014] In a fourth embodiment, the invention is directed toward a
composition of matter comprising a polymer derived from at least two
monomers: acrylic-x and an alkylamine, and wherein said acrylic-x has the
following formula:

##STR00002##

wherein X═OH and salts thereof or NHR2 and wherein R1 and
R2 is H or an alkyl or aryl group, wherein the molecular weight of
said polymer is between 500 to 200,000, and wherein said polymer is
modified to contain a functional group capable of scavenging at least one
metal-comprising composition; and an iron salt. The composition may be
comprised additionally of a polydithiocarbamic compound of at least one
polythiocarbamic material, and the polymer may be comprised of a
polydithiocarbamic compound.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The benefits and advantages of the present invention will become
more readily apparent to those of ordinary skill in the relevant art
after reviewing the following detailed description and accompanying
drawings, wherein:

[0016] FIG. 1 is a graph demonstrating the positive effects of Chemistry 1
on decreased selenium concentration and decreased oxidation-reduction
potential in the aqueous phase of a flue gas wet scrubber process; and

[0017]FIG. 2 is a graph demonstrating the positive effects of Chemistry 2
on decreased selenium concentration and decreased oxidation-reduction
potential in the aqueous phase of a flue gas wet scrubber process.

DETAILED DESCRIPTION OF THE INVENTION

[0018] While the present invention is susceptible of embodiment in various
forms, there will hereinafter be described a presently preferred
embodiment with the understanding that the present disclosure is to be
considered an exemplification of the invention and is not intended to
limit the invention to the specific embodiment illustrated.

[0019] It should be further understood that the title of this section of
this specification, namely, "Detailed Description of the Invention,"
relates to a requirement of the United States Patent Office, and does not
imply, nor should be inferred to limit the subject matter disclosed
herein.

[0020] The present invention documents the unexpected results obtained
from the use of certain chemistries, which unexpectedly reduced selenium
concentration nearly ten-fold in water phase blowdown of a flue gas wet
scrubber process. While not wishing to be bound by a particular
mechanism, through the addition of the chemistries within the flue gas
wet scrubber process, the chemistries have the opportunity to capture the
selenite before it has a chance to further oxidize to selenate. Selenate
is difficult to remove from the water phase.

[0021] Additionally, the chemistries have also proved to be advantageous
in minimizing corrosion in flue gas wet scrubber systems. Particularly,
the chemistries have helped minimize corrosion in flue gas wet scrubber
systems that are constructed of 2205 alloy. It was unexpectedly found
that these chemistries, when circulated in a flue gas wet scrubber
process with flue gas wet scrubber liquor, reduced the
oxidation-reduction potential ("ORP") within the flue gas wet scrubber
process. The reduction of ORP reduces the tendency for corrosion.
Examples showing the reduction are provided below.

[0022] It is important to note that, while ORP is not exactly the same as
corrosion potential, the two numbers track each other. ORP is an
indication of the oxidative or reductive nature of the environment.
Corrosion potential is the oxidative or reductive nature at the surface
of a specific metal. Therefore, the corrosion potential generally
reflects the ORP, but the two values are not the same. However, the ORP
trend would typically indicate the corrosion potential trend. Hence, an
observed reduction in ORP is expected to result in a reduction in
corrosion potential. For the invention at hand, it was unexpected to see
the addition of the chemistries, chelating agents for heavy metal
removal, to result in a reduction in ORP value and thereby a reduction in
corrosion rate.

[0025] In an embodiment, the fuel is selected from the group consisting of
coal, reclaimed coal, natural gas, industrial waste, a gasified waste
product, biomass, and any combination thereof.

Chemistry 1:

[0026] Chemistry 1 is a water-soluble ethylene dichloride ammonia polymer
having a molecular weight of from 500 to 10,000, which contains from 5 to
55 mole % of dithiocarbamate salt groups. Chemistry 1 may additionally
comprise a transition metal salt, which may be an iron salt. The positive
effects of Chemistry 1 on both reduction of selenium in the aqueous phase
and reduction in oxidation-reduction potential are shown in FIG. 1. The
ethylene dichloride-ammonia polymers are prepared by the reaction of
ethylene dichloride and ammonia. The starting ethylene dichloride-ammonia
polymers generally have a molecular weight range of 500-100,000. In a
preferred embodiment the molecular weight is 1,500 to 10,000, with the
most preferred molecular weight range being 1,500 to 5,000. The copolymer
of this invention is produced using methods presented in U.S. Pat. Nos.
4,731,187; 5,500,133; or 5,658,487 that are examples of said copolymers
available for use in the claimed invention. The copolymer is produced by
the reaction of the polyamines or polyimines with carbon disulfide to
produce polydithiocarbamic acid or its salts. Such reaction is preferably
carried out in a solvent such as water or alcohol at a temperature of
from 30° and 100° C. for periods of time ranging between 1
and 10 hours. Good conversion is obtained at temperatures between
40° and 70° C. for 2 to 5 hours. These reaction conditions
apply to the modification of ethylene dichloride-ammonia polymers
described previously.

[0027] The mole % of dithiocarbamate salt groups in the finished polymer
generally is within the range of 5 to 55%. The preferred range is 20 to
55 mole %, with the most preferred range being about 30 to 55 mole %.

[0028] The salts include but are not limited to alkaline and alkali earth
such as sodium, lithium, potassium or calcium. The chemistry may include
at least one transition metal salt, which may be an iron salt.

[0029] The scrubber processes currently used in the industry include spray
towers, jet bubblers, and co-current packed towers as examples. These
types of air quality control devices ("AQCDs") are provided as examples
and are not meant to represent or suggest any limitation. The
water-soluble copolymer may be added to virgin limestone or lime slurry
prior to addition to the scrubber, the recirculation loop of the scrubber
liquor, or the "low solids" return to the scrubber from the scrubber
purge stream.

[0030] Typically, the copolymer is applied at a ratio of 1:1 to 2000:1
weight copolymer to weight of selenium being captured. The preferred
ratio is from 5:1 to 1000:1 and the most preferred range is from 5:1 to
500:1.

[0031] In general the polydithiocarbamic acid compounds may be introduced
into the scrubber and thereby into the scrubber liquor via several
routes. The following will serve as just some of the variations that are
available to introduce the compounds into the scrubber liquor. The
scrubber liquor is defined as the water-based dispersion of calcium
carbonate (limestone) or calcium oxide (lime) used in a wet flue gas
scrubber ("FGS," also known as a wet flue gas desulfurizer, or "FGD") to
capture SOx emissions. The liquor may also contain other additives
such as magnesium and low-molecular weight organic acids, which function
to improve the sulfur, capture. One example of such an additive is a
mixture of low-molecular weight organic acids known as dibasic acid
("DBA"). DBA consists of a blend of adipic, succinic, and glutaric acids.
Each of these organic acids can also be used individually. In addition,
another low-molecular weight organic acid that can be used to improve
sulfur capture in a wet scrubber is formic acid. Finally, the scrubber
liquor will also contain byproducts of the interaction between the lime
or limestone and sulfur species, which leads to the presence of various
amounts of calcium sulfite or calcium sulfate. The scrubber liquor
includes but is not limited to the make-up liquor, return liquor, the
reclaimed liquor, virgin liquor and liquor injected directly into flue
gases.

[0032] Another addition point for the polydithiocarbamic compounds of this
invention to the wet scrubber is via the "low solids" liquor return. A
portion of the liquor is usually continuously removed from the scrubber
for the purpose of separating reaction byproducts from unused lime or
limestone. One means of separation that is currently used is
centrifugation. In this process the scrubber liquor is separated into a
"high solids" and "low solids" stream. The high solids stream is diverted
to wastewater processing. The low solids fraction returns to the wet
scrubber and can be considered "reclaimed" dilute liquor. The
polydithiocarbamic acid compounds of this invention can conveniently be
added to the reclaimed low solids stream prior to returning to the
scrubber.

[0033] Another feed liquor found in the operation of a wet flue gas
desulfurizer is called "virgin liquor." Virgin liquor is the water-based
dispersion of either lime or limestone prior to exposure to flue gas and
is used to added fresh lime or limestone while maintaining the scrubber
liquor level and efficiency of the wet FGD. This is prepared by
dispersing the lime or limestone in water. Here the polydithiocarbamic
acid compounds can be added either to the dispersion water or the virgin
liquor directly.

[0034] Finally, some wet scrubber installations use scrubber liquor and/or
water (fresh or recycled) injected directly into the flue gas prior to
the scrubber for the purpose of controlling relative humidity of the flue
gas or its temperature. The excess liquid is then carried into the wet
scrubber. Here also are two potential addition points for the
introduction of the polydithiocarbamic acid compounds of the present
invention.

[0035] The addition of the polydithiocarbamic acid compounds can be made
in any of these locations, wholly or fractionally (i.e. a single feed
point or multiple feed points), including but not limited to the make-up
water for the lime or limestone slurry or the scrubber liquor.

Chemistry 2:

A. Composition

[0036] The present disclosure provides for a composition comprising a
polymer derived from at least two monomers: acrylic-x and an alkylamine,
wherein said acrylic-x has the following formula:

##STR00003##

wherein X═OR, OH and salts thereof, or NHR2 and wherein R1
and R2 is H or an alkyl or aryl group, wherein R is an alkyl or aryl
group, wherein the molecular weight of said polymer is between 500 to
200,000, and wherein said polymer is modified to contain a functional
group capable of scavenging one or more compositions containing one or
more metals.

[0037] The metals can include zero valent, monovalent, and multivalent
metals. The metals may or may not be ligated by organic or inorganic
compounds. Also, the metals can be radioactive and nonradioactive.
Examples include, but are not limited to, transition metals and heavy
metals. Specific metals can include, but are not limited to: copper,
nickel, zinc, lead, mercury, cadmium, silver, iron, manganese, palladium,
platinum, strontium, selenium, arsenic, cobalt and gold. The molecular
weight of the polymers can vary. For example, the target
species/application for the polymers can be one consideration. Another
factor can be monomer selection. Molecular weight can be calculated by
various means known to those of ordinary skill in the art. For example,
size exclusion chromatography, as discussed in the examples below can be
utilized.

[0038] When molecular weight is mentioned, it is referring to the
molecular weight for the unmodified polymer, otherwise referred to as the
polymer backbone. The functional groups that are added to the backbone
are not part of the calculation. Thus the molecular weight of the polymer
with the functional groups can far exceed the molecular weight range.

[0039] In one embodiment, the molecular weight of the polymer is from
1,000 to 16,000.

[0040] In another embodiment, the molecular weight of said polymer is from
1,500 to 8,000. Various functional groups can be utilized for metal
scavenging. The following phraseology would be well understood by one of
ordinary skill in the art: wherein said polymer is modified to contain a
functional group capable of scavenging one or more compositions
containing one or more metals. More specifically, the polymer is modified
to contain a functional group that can bind metals.

[0041] In one embodiment, the functional group contains a sulfide
containing chemistry.

[0042] In another embodiment, the functional group is a dithiocarbamate
salt group.

[0044] The molar amounts of the functional group relative to the total
amines contained in the unmodified polymer can vary as well. For example,
the reaction of 3.0 molar equivalents of carbon disulfide to a 1.0:1.0
mole ratio acrylic acid/TEPA copolymer, which contains 4 molar
equivalents of amines per repeat unit after polymerization, will result
in a polymer that is modified to contain 75 mole % dithiocarbamate salt
group. In other words, 75% of the total amines in the unmodified polymer
has been converted to dithiocarbamate salt groups.

[0045] In one embodiment, the polymer has between 5 to 100 mole % of the
dithiocarbamate salt group. In a further embodiment, the polymer has from
25 to 90 mole % of the dithiocarbamate salt group. In yet a further
embodiment, the polymer has from 55 to 80 mole % of the dithiocarbamate
salt group.

[0046] Monomer selection will depend on the desired polymer that one of
ordinary skill in the art would want to make.

[0047] The alkylamines may vary in kind.

[0048] In one embodiment, the alkylamine is at least one of the following:
an ethyleneamine, a polyethylenepolyamine, ethylenediamine (EDA),
diethylenetriamine (DETA), triethylenetetraamine (TETA) and tetra
ethylenepetamine (TEPA) and pentaethylenehexamine (PEHA).

[0049] The acrylic-x monomer group can vary as well.

[0050] In another embodiment, the acrylic-x is at least one of the
following: methyl acrylate, methyl methacrylate, ethyl acrylate, and
ethyl methacrylate, propyl acrylate, and propyl methacrylate.

[0051] In another embodiment, the acrylic-x is at least one of the
following: acrylic acid and salts thereof, methacrylic acid and salts
thereof, acrylamide, and methacrylamide.

[0052] The molar ratio between monomers that make up the polymer,
especially acrylic-x and alkylamine can vary and depend upon the
resultant polymer product that is desired. The molar ratio used is
defined as the moles of acrylic-x divided by the moles of alkylamine.

[0053] In one embodiment, the molar ratio between acrylic-x and alkylamine
is from 0.85 to 1.5.

[0054] In another embodiment, the molar ratio between acrylic-x and
alkylamine is from 1.0 to 1.2.

[0055] Various combinations of acrylic-x and alkylamines are encompassed
by this invention as well as associated molecular weight of the polymers.

[0056] In one embodiment, the acrylic-x is an acrylic ester and the
alkylamine is PEHA or TEPA or DETA or TETA or EDA. In a further
embodiment, the molar ratio between acrylic-x and alkylamine is from 0.85
to 1.5. In yet a further embodiment, the molecular weight can encompass
ranges: 500 to 200,000, 1,000 to 16,000, or 1,500 to 8,000. In yet a
further embodiment, the acrylic ester can be at least one of the
following: methyl acrylate, methyl methacrylate, ethyl acrylate, and
ethyl methacrylate, propyl acrylate, and propyl methacrylate, which is
combined with at least one of the alklyamines, which includes PEHA or
TEPA or DETA or TETA or EDA. In yet a further embodiment, the resulting
polymer is modified to contain the following ranges of dithiocarbamate
salt groups: 5 to 100 mole %, 25 to 90 mole %, 55 to 80 mole %.

[0057] In another embodiment, the acrylic-x is an acrylic amide and the
alkylamine is TEPA or DETA or TETA or EDA. In a further embodiment, the
molar ratio between acrylic-x and alkylamine is from 0.85 to 1.5. In yet
a further embodiment, the molecular weight can encompass ranges: 500 to
200,000, 1,000 to 16,000, or 1,500 to 8,000. In yet a further embodiment,
the acrylic amide can be at least one or a combination of acrylamide and
methacrylamide, which is combined with at least one of the alklyamines,
which includes PEHA or TEPA or DETA or TETA or EDA. In yet a further
embodiment, the resulting polymer is modified to contain the following
ranges of dithiocarbamate salt groups: 5 to 100 mole %, 25 to 90 mole %,
or 55 to 80 mole %.

[0058] In another embodiment, the acrylic-x is an acrylic acid and salts
thereof and the alkylamine is PEHA or TEPA or DETA or TETA or EDA. In a
further embodiment, the molar ratio between acrylic-x and alkylamine is
from 0.85 to 1.5. In yet a further embodiment, the molecular weight can
encompass ranges: 500 to 200,000, 1,000 to 16,000, or 1,500 to 8,000. In
yet a further embodiment, the acrylic acid can be at least one or a
combination of acrylic acid or salts thereof and methacrylic acid or
salts thereof, which is combined with at least one of the alklyamines,
which includes TEPA or DETA or TETA or EDA. In yet a further embodiment,
the resulting polymer is modified to contain the following ranges of
dithiocarbamate salt groups: 5 to 100 mole %, 25 to 90 mole %, or 55 to
80 mole %.

[0059] Additional monomers can be integrated into the polymer backbone
made up of constituent monomers acrylic-x and alkylamine. A condensation
polymer reaction scheme can be utilized to make the basic polymer
backbone chain. Various other synthesis methods can be utilized to
functionalize the polymer with, for example, dithiocarbamate and/or other
non-metal scavenging functional groups. One of ordinary skill in the art
can functionalize the polymer without undue experimentation.

[0060] Moreover, the composition of the present invention can be
formulated with other polymers such as those disclosed in U.S. Pat. No.
5,164,095, herein incorporated by reference, specifically, a water
soluble ethylene dichloride ammonia polymer having a molecular weight of
from 500 to 100,000 which contains from 5 to 50 mole % of dithiocarbamate
salt groups. In one embodiment, the molecular weight of the polymer is
from 1500 to 10,000 and contains 15 to 50 mole % of dithiocarbamate salt
groups. In a preferred embodiment, the molecular weight of the polymer is
from 1500 to 5000 and contains 30 to 55 mole % of dithiocarbamate salt
groups. Also, the composition of the present invention can be formulated
with other small molecule sulfide precipitants such as sodium sulfide,
sodium hydrosulfide, TMT-15® (sodium or calcium salts of
trimercapto-S-triazine; Evonik Industries Corporation 17211 Camberwell
Green Lane, Houston, Tex. 77070, USA), dimethyldithiocarbamate and
diethyldithiocarbamate.

B. Dosage

[0061] The dosage of the disclosed polymers for use may vary. The
calculation of dosage amounts can be done without undue experimentation.

[0062] Process medium quality and extent of process medium treatment are a
couple of factors that can be considered by one of ordinary skill in the
art in selecting dosage amount. A jar test analysis is a typical example
of what is utilized as a basis for determining the amount of dosage
required to achieve effective metals removal in the context of a process
water medium, e.g. wastewater.

[0063] In one embodiment, the amount of modified polymer of the invention
capable of effectively removing metals from contaminated waters is
preferably within the range of 0.2 to 2 moles of dithiocarbamate per mole
of metal. More preferably, the dosage is 1 to 2 moles of dithiocarbamate
per mole of metal contained in the water. According to one embodiment of
the invention, the dosage of metal removal polymer required to chelate
and precipitate 100 ml of 18 ppm soluble copper to about 1 ppm or less
was 0.011 gm (11.0 mg) of polymer. The metal polymer complexes formed are
self-flocculating and quickly settle. These flocculants are easily
separated from the treated water.

[0064] In the context of applying the polymer to a gas system, such as a
flue gas, the polymer can be dosed incrementally and capture rates for a
particular metal, e.g. such as mercury, can be calculated by known
techniques in the art.

C. Methods of Use

[0065] The present disclosure also provides for a method of removing
selenium from a medium containing selenium which comprises the steps of:
(a) treating said medium containing metals with a composition comprising
a polymer derived from at least two monomers: acrylic-x and an
alkylamine, wherein said acrylic-x has the following formula:

##STR00004##

wherein X═OR, OH and salts thereof, or NHR2 and wherein R1
and R2 is H or an alkyl or aryl group, wherein R is an alkyl or aryl
group, wherein the molecular weight of said polymer is between 500 to
200,000, and wherein said polymer is modified to contain a functional
group capable of scavenging one or more compositions containing one or
more metals; and (b) collecting said treated metals.

[0066] The compositions as described above are incorporated into this
section and can be applied within the claimed methodologies encompassed
by this invention.

[0067] Mediums containing selenium can vary and include at least one of
the following wastewater streams, liquid hydrocarbonaceous streams, flue
gas streams, flyash, and other particulate matter. Various processing
steps can be coupled with metals removal, including, but not limited to
filtration steps and/or air quality control devices, e.g. baghouses and
electrostatic precipitators and other air quality control devices.

[0068] Mediums containing a liquid phase medium/a medium containing a
liquid phase are one target for the claimed invention.

[0069] In one embodiment, the medium is a process stream containing water,
e.g. wastewater or wastewater from a power plant or industrial setting
(power plant, mining operation, waste incineration, and/or manufacturing
operation).

[0070] In another embodiment, the medium is a liquid hydrocarbonaceous
stream common in petroleum refining processes or petrochemical processes.
Examples include streams from these processes that contain petroleum
hydrocarbons such as petroleum hydrocarbon feedstocks including crude
oils and fractions thereof such as naphtha, gasoline, kerosene, diesel,
jet fuel, fuel oil, gas oil vacuum residual, etc or olefinic or napthenic
process streams, ethylene glycol, aromatic hydrocarbons, and their
derivatives.

[0071] In another embodiment, additional chemistries, flocculants and/or
coagulants can be utilized in conjunction with the chemistry encompassed
by this invention. The chemistries applied to a medium containing metals
can vary, including, the addition of at least one of the following:
cationic polymers, anionic polymers, amphoteric polymers, and
zwitterionic polymers.

[0072] In another embodiment, the method of this invention further
comprises an additional treatment to the process stream with a complexing
amount of a water soluble ethylene dichloride ammonia polymer having a
molecular weight of from 500 to 100,000 which contains 5 to 50 mole % of
dithiocarbamate salt groups to form a complex of these metals, e.g. heavy
metals. In a further embodiment, the molecular weight of the polymer is
from 1500 to 10,000 and contains 15 to 50 mole % of dithiocarbamate salt
groups. In a preferred embodiment, the molecular weight of the polymer is
from 1500 to 5000 and contains 30 to 55 mole % of dithiocarbamate salt
groups.

[0073] In another embodiment, the polymer treatment and additional
treatment are added in a ratio of 1:1.

[0074] Mediums containing a gas phase medium/a medium containing a gas
phase are another target for the claimed invention. In addition,
processes containing a liquid and/or gas phase medium are encompassed by
this invention as well.

[0075] In another embodiment, the medium is part of a heat generating
system, e.g. a flue gas stream.

[0076] In another embodiment, the heat generating system is at least one
of the following: a combustion system; a power plant combustion system; a
coal combustion system; a waste incineration system; a kiln; a kiln for
mining or cement operations; and an ore processing system.

[0077] In another embodiment, the method of this invention further
comprises applying an oxidizing agent to a heat generating system. In a
further embodiment, the oxidizing agent is applied prior to said polymer
treatment.

[0078] In a yet a further embodiment, a multiphase treatment protocol for
a process involves treating a gas and a liquid, e.g., one or more metals
in a gas such as mercury and one or more metal in a liquid. This can
involve the polymer treatment and additional treatment as described
above.

[0079] In yet a further embodiment, the oxidizing agent is at least one of
the following: a thermolabile molecular halogen, calcium bromide, or a
halogen containing compound. In yet a further embodiment, this invention
further comprises applying an oxidizing agent to the flue gas; optionally
wherein said oxidizing agent oxidizes a target species at a temperature
of 500° C. or greater or a temperature where the oxidant is
capable of oxidizing molecular mercury that exists in a process that
generates mercury; optionally wherein said target species is elemental
mercury or derivatives thereof; and optionally wherein said oxidizing
agent is at least one of the following: a thermolabile molecular halogen,
calcium bromide, or a halogen containing compound. Mercury oxidant
methodologies are described in U.S. Pat. Nos. 6,808,692 and 6,878,358,
which are herein incorporated by reference.

[0080] In another embodiment, the polymer treatment occurs at a
temperature 300° C. or below, preferably 250° C. or below.

[0081] The invention is illustrated by the proceeding descriptions and the
following examples which are not meant to limit the invention unless
otherwise stated in the claims appended hereto.

EXAMPLES

[0082] The foregoing may be better understood by reference to the
following examples, which are intended to illustrate methods for carrying
out the invention and are not intended to limit the scope of the
invention.

[0083] It should be understood that various changes and modifications to
the presently preferred embodiments described herein will be apparent to
those skilled in the art. Such changes and modifications can be made
without departing from the spirit and scope of the invention and without
diminishing its intended advantages. It is therefore intended that such
changes and modifications be covered by the appended claims.

Chemistry 1: Examples 1-6

Example 1

[0084] A sample of scrubber water that was treated by vacuum filter. The
objective was to remove mercury. The sample was investigated for mercury
removal using design of experiments with two variables pH and dosage.

[0085] The results showed that mercury levels of less than 0.5 ppb in the
treated water was achieved at various pHs at a reasonable product
dosages. This work demonstrated that the product did achieve mercury
capture from wet FGD liquors. The lower detection limit of the analytical
method was 0.5 ppb.

[0088] The zeolite was a spent commercial catalyst. The fly ash sample was
obtained from a coal-fired power plant. The fly ash sample was composed
of 93% ash content with 6% residual carbon and 1% residual sulfur. These
results clearly show that neither fly ash nor zeolites significantly
reduce the ionic mercury content.

Example 3

[0089] A synthetic FGD scrubber liquor was prepared by dissolving 12.58 g
of calcium chloride dihydrate, CaCl2.2H2O, in 400 mL of
deionized water. The resulting solution was 214 mM in calcium chloride
dihydrate leading to 15,000 ppm chloride and 8560 ppm calcium in
solution. The solution was split into two equal portions. To 200 mL of
solution was added 164 μL of 0.61 mM mercury nitrate solution to yield
a solution containing 130 μg/L of ionic mercury. This solution was
treated with 27.4 g of calcium sulfate dihydrate or 18 weight percent.
The solution was mixed and split into two portions. The smaller portion,
75 g total, was treated with the polydithiocarbamic acid compound at a
5:1 product to mercury weight ratio. The polydithiocarbamic acid compound
product was a 30% active water miscible solution. The two portions were
agitated separately with a magnetic stir bar for 12 hours. After which
time, the suspension was filtered using a Pall Life Sciences GN-6
Metricel 0.45μ membrane filter (P/N 63069). The filtrate was analyzed
for mercury.

[0090] A second portion, 200 g, of calcium chloride dihydrate solution was
treated with 82 μL of 0.61 mM mercuric nitrate solution to yield a
solution containing 78.3 μg of ionic mercury. Again this solution was
treated with 27.4 g of calcium sulfate, dihydrate to yield a slurry
containing 18% by weight. As before, this sample was split into two
solutions, the minor portion, 75 g, was treated with the
polydithiocarbamic acid compound product at a 5:1 product weight to
mercury weight ratio. After further mixing for 12 hours using a magnetic
stir bar, the dispersions were filtered using a Pall Life Sciences GN-6
Metricel 0.45μ membrane filter (P/N 63069). The filtrate was analyzed
for mercury.

[0092] It is clear from this example that the polydithiocarbamic acid
compound of this invention removes the ionic mercury from the liquid
phase. The gypsum solids for the above samples were submitted for TGA
(Thermogravimetric Analysis) in order to observe any decomposition or
release of mercury. All the thermographs were identical exhibiting only
the loss of associated and bound water between room temperature and
170° C. Above this temperature no further decomposition could be
observed. This indicates that once the complex is formed, it does not
decompose under normal FGD scrubber operation.

Example 4

[0093] A general stock solution was prepared containing 0.214M calcium
chloride dihydrate by dissolving 220 g of CaCl2.2H2O in 7 L of
deionized water. To this was added 74 μL of 61 mM mercury nitrate
solution to yield a solution containing 136 μg/L. This solution was
divided into two portions. The first portion was mixed with enough
calcium sulfate dihydrate to yield slurry at 18% by weight-dispersed
solids. The second portion was mixed with enough calcium sulfate
dihydrate to yield a 21% by weight slurry.

[0094] Organic acids are used in many wet FGD scrubbers to improve the
SOx removal efficiency as well as the limestone or lime utilization.
In most cases, a by-product stream known in the industry as Dibasic Acid
or DBA is the product of choice. DBA is a mixture of adipic acid (aka
hexanedioic acid), succinic acid (aka butanedioic acid) and glutaric acid
(aka pentaedioic acid). For the purposes of this example, a "synthetic"
DBA was prepared using an equal molar ratio of adipic and succinic acids.
The adipic acid can be obtained from Mallinckrodt Chemicals, Cat No.
MK180159. The succinic acid can be obtained from J. T. Baker, reagent
grade, Cat. No. JT0346-5. The solutions were spiked with the equal molar
ratio acids to produce 332 and 100 ppm total acid concentrations.

[0095] The polydithiocarbamic acid compound of the current invention was
added at a product to mercury weight ratio of 4.5:1 and 1:1 respectively
with or without the synthetic DBA present in the slurry. The order of
addition was kept to the following: synthetic DBA then the
polydithiocarbamic acid compound of this invention. Once the various
additives have been introduced into the slurry, it is mixed for an
additional 15 to 20 minutes with a magnetic stir bar. After this time,
the slurry is filtered using a Pall Life Sciences GN-6 Metricel 0.45μ,
membrane filter (P/N 63069). The filtrate is subsequently analyzed.

[0097] DTCP is the polydithiocarbamic acid compound of this invention. See
above for the definition of synthetic DBA, aka "Syn DBA".

[0098] The results in the table above clearly show that the presence of
organic acids in the scrubber liquor does not interfere with the
performance of the polydithiocarbamic acid compound of this invention
regarding complexing mercury in the liquid phase. The results also
confirm that the copolymer interacts with and removes ionic mercury from
the liquid phase to below 500 parts per trillion.

Example 5

[0099] Three additives were tested in a bench-scale wet scrubber with a
gas flow of 1-cfm. One additive, TMT-15 is currently used to control
mercury emissions from incinerators. The polydithiocarbamic acid
compound, sodium salt used is an embodiment of the claimed invention.

[0100] The bench-scale unit allows for the use of a simulated flue gas
composed of SO2, NOx, HCl, CO2, oxygen and nitrogen.
Moisture is controlled by exposing a portion of the oxygen, carbon
dioxide, and nitrogen to water saturators. The flue gas composition used
in the study consisted of 15-25 μg/Nm3 HgCl2, 12% CO2,
3% O2, 1000 ppm SO2, 15 ppm HCl, no NOx, the balance
nitrogen. The flow rate was 28 L/min. The sorbent solution or scrubber
liquor was maintained at a temperature of 55° C. and consisted of
100 mM sodium chloride, and 10 mM sodium sulfate (initial concentration)
with a pH of 5.0. The sulfite concentration was controlled at 5 mM by the
addition of hydrogen peroxide to the sorbent solution. The pH of the
scrubber liquor was maintained by the addition of NaOH. In each case, the
appropriate amount of additive was introduced into the scrubber liquor
just prior to the injection of 0.5 μM HgCl2 as a solution of 0.5
mM HgCl2 and after the system had reached equilibrium.

[0101] The bench-scale scrubber uses a bubbler type gas contactor. The gas
contact vessel sits on top of the scrubber liquor reaction vessel so that
the liquor returns to the reactor vessel via gravity drainage. The liquor
is recirculated into the scrubber via a recirculation pump to maintain a
constant liquid/gas ratio. The pH is monitored both in the scrubber and
in the reaction vessel. The pH of the reaction vessel is maintained by
addition of sodium hydroxide solution. The reaction vessel is mixed via
magnetic stirring. A flow-through cell and spectrophotometer was used to
monitor sulfite concentration in the scrubber liquor via a modification
of a method reported by M. W. Scoggins, Analytical Chemistry, 42(9),
1091(1970). The results were used to automatically control the addition
of hydrogen peroxide so as to maintain the target sulfite concentration.
Oxidized mercury is added to the gas by passing a portion of the dry
nitrogen gas through a mercury diffusion cell. About 5% of the total
mercury introduced in this way was elemental. Two separate CVAAS (Cold
Vapor Atomic Adsorption Spectroscopy) instruments monitored respectfully
the flue gas inlet and the scrubber outlet. The mercury re-emissions were
calculated as follows:

[0103] It is clear from these bench-scale results that the
polydithiocarbamic acid compound of the current invention successfully
controls the re-emission of mercury from a wet FGD and does so more
efficiently than the current art.

Example 6

[0104] A study was undertaken at a commercial site consisting of a 512 MW
boiler equipped with cold-side electrostatic precipitator ("ESP") and a
flue gas wet scrubber process comprised of limestone forced oxidation
("LSFO") wet FGD system. The boiler fired high-sulfur sulfur bituminous
coal. Samples of the LSFO wet FGD liquor were collected during the
demonstration under the noted conditions and analyzed for total selenium.
The results are presented in the table below as well as FIG. 1.

[0106] The untreated unit was burning the same fuel during this commercial
test. Chemistry 1 was applied to the treated unit. Two samples were taken
during different periods of the demonstration while the technology was
applied. The disclosed technology was turned off for 18 hours (i.e.
Condition Additive Off shown above) prior to sampling. Then Chemistry 1
was reapplied to obtain the final condition, i.e. additive reapplied.

[0107] As can be seen in the previous table, the untreated unit total
selenium varied from 585 to 676 μg/L. The application of the disclosed
technology resulted in 65% reduction of selenium in the scrubber liquor.
The efficacy of the technology is further demonstrated by the cessation
of the application of the technology resulting in an observed increase in
total selenium which was again reduced by reapplication of the
technology. It is clear from these results that Chemistry 1 reduces
selenium concentration in wet FGD liquor.

Chemistry 2: Examples 7-11:

Example 7

Methyl Acrylate/Tetraethylenepentamine Polymer Backbone which is then
Functionalized with a Dithiocarbamate Group

[0109] Tetraethylenepentamine (TEPA) (18.275 weight %) was charged into a
glass reactor fitted with a mechanical stirrer and a condenser. While
purging the headspace with nitrogen and stirring, methyl acrylate (16.636
weight %) was added dropwise over 30 min where the temperature was
maintained between 25-31° C. during the addition and for 1 h after
the addition was finished. Next, a second charge of TEPA (18.275 weight
%) was performed and the resulting reaction mixture was heated to
130° C. This temperature was held for ˜3 h while collecting
the condensate in a Dean-Stark trap. At this time, the polymer melt was
allowed to cool to 120° C. and then slowly diluted with deionized
(DI) water (46.814 weight %) keeping the temperature above 90° C.
during the dilution. The resulting ˜50 weight % polymer solution
was then cooled to room temperature. Weight average molecular weight of
the polymer was determined to be 7,500 using a size exclusion
chromatography method and polysaccharide standards.

[0112] Tetraethylenepentamine (TEPA) (37.556 weight %) and sulfuric acid
(0.199 weight %) was charged into a glass reactor fitted with a
mechanical stirrer and a condenser. While purging the headspace with
nitrogen and stirring, acrylic acid (14.304 weight %) was added dropwise
over 30 min where the temperature was maintained between 130-140°
C. during the addition, allowing the exotherm from the acid base reaction
to reach the desired temperature. Next the resulting reaction mixture was
heated to 160° C. This temperature was held for 4.5 h while
collecting the condensate in a Dean-Stark trap. At this time, the polymer
melt was allowed to cool to 120° C. and then slowly diluted with
DI water (47.941 weight %) keeping the temperature above 90° C.
during the dilution. The resulting ˜50 weight % polymer solution
was then cooled to room temperature. Weight average molecular weight of
the polymer was determined to be 4,700 using a size exclusion
chromatography method and polysaccharide standards.

b. Dithiocarbamate Polymer Preparation

[0113] The second step involved adding the acrylic acid/TEPA polymer
(31.477 weight %), DI Water (36.825 weight %), and Dowfax 2A1(0.118
weight %) to a round bottom flask fitted with a mechanical stirrer. Next,
a 50% NaOH solution (8.393 weight %) was added to the stirring reaction
mixture. Once the mixture was heated and maintained at 40° C.,
carbon disulfide (14.794 weight %) was added drop-wise over 2 h. One hour
within the carbon disulfide addition, another amount of 50% NaOH (8.393
weight %) was charged. The reaction mixture was maintained at 40°
C. for an additional 2 h. Finally, the reaction was cooled to room
temperature and filtered though filter paper to obtain ˜35 weight %
polymeric dithiocarbamate product.

Example 9

a. Acrylamide/Tetraethylenepentamine Polymer Backbone Synthesis

[0114] Tetraethylenepentamine (TEPA) (14.581 weight %) was charged into a
glass reactor fitted with a mechanical stirrer and a condenser. While
purging the headspace with nitrogen and stirring, a 48.6% acrylamide
solution (30.441 weight %) was added dropwise over 1 h during which the
desired temperature was reached and was maintained between 65-75°
C. After the acrylamide charge, the temperature was maintained for an
additional 1 h. Next, a second charge of TEPA (14.581 weight %) was
performed and the resulting reaction mixture was heated to 160° C.
while collecting the distilled water via a Dean-Stark trap. This
temperature was held for ˜4 h while continuing to collect the
condensate in a Dean-Stark trap and trapping the released ammonia side
product. At this time, the polymer melt was allowed to cool to
120° C. and then slowly diluted with DI water (40.397 weight %)
keeping the temperature above 90° C. during the dilution. The
resulting ˜50 weight % polymer solution was then cooled to room
temperature. Weight average molecular weight of the polymer was
determined to be 4500 using a size exclusion chromatography method and
polysaccharide standards.

b. Dithiocarbamate Polymer Preparation

[0115] The second step involved adding the acrylamide/TEPA polymer (34.004
weight %), DI Water (36.518 weight %), and Dowfax 2A1(0.122 weight %) to
a round bottom flask fitted with a mechanical stirrer. Next, a 50% NaOH
solution (7.763 weight %) was added to the stirring reaction mixture.
Once the mixture was heated and maintained at 40° C., carbon
disulfide (13.830 weight %) was added drop-wise over 2 h. One hour within
the carbon disulfide addition, another amount of 50% NaOH (7.763 weight
%) was charged. The reaction mixture was maintained at 40° C. for
an additional 2 h. Finally, the reaction was cooled to room temperature
and filtered though filter paper to obtain ˜35 weight % polymeric
dithiocarbamate product.

Example 10

[0116] A sample of scrubber water was treated and then allowed to settle.
A supernatant sample was taken and measured for total mercury content and
then filtered for dissolved mercury content. The objective was to remove
mercury. The samples were investigated for mercury removal relative to
the dosage of Chemistry 2 in wet FGD liquors from two different
coal-fired power plants.

[0117] The results show that a mercury level of less than 0.5 ppb in the
treated water was achieved at reasonable product dosages. This work
demonstrated that the polymer achieved mercury capture from wet FGD
liquors. The lower detection limit of the analytical method was 0.010
ppb. The efficient/effective action of mercury capture by Chemistry 2 can
be extrapolated to its ability to successfully prevent mercury
re-emission within an operating wet FGD.

[0118] A sample of scrubber water was treated at temperatures typical of
wet FGD operations (50° C.), measured with an ORP electrode and
then filtered. The objective was to investigate the effect that Chemistry
2 has on the ORP of the liquor and selenium removal relative to the
dosage.

[0119] The results show that Chemistry 2 is capable of removing selenium
from wet FGD liquor. In this case, 56% removal of selenium was achieved.
This work also demonstrated that Chemistry 2 can successfully lower the
ORP of the liquor, thus reducing the tendency for corrosion within a wet
FGD scrubber. Graphical results of these tests is illustrated in FIG. 2.

[0120] All patents referred to herein, are hereby incorporated herein by
reference, whether or not specifically done so within the text of this
disclosure.

[0121] In the present disclosure, the words "a" or "an" are to be taken to
include both the singular and the plural. Conversely, any reference to
plural items shall, where appropriate, include the singular.

[0122] From the foregoing it will be observed that numerous modifications
and variations can be effectuated without departing from the true spirit
and scope of the novel concepts of the present invention. It is to be
understood that no limitation with respect to the illustrated specific
embodiments or examples is intended or should be inferred. The disclosure
is intended to cover by the appended claims all such modifications as
fall within the scope of the claims.